codebehind best practices

I've got a set of 3 aspx pages that all follow a certain template. They all contain a repeater, dropdownlist and 4 navigation buttons. I'm using the same codebhind for all 3 pages to handle click events and bind the data in the Page_Load. However, on some pages, I need aditional coding in the Page_Load. If I explicitly include a Page_Load in a <script runat="server"></script> block on this page, it overrides the Page_Load that is contained in the codebhind, so I'm forced to duplicate the Page_Load code in the codebehind and add the extra code required for this specific page... What can I do to prevent duplicating the data? Also, is it possible to have multiple files for the codebehind? Keep in mind I want to follow best practices...

First off you should never have an inline page_load event and one in the codebehind, can't believe it let you do that and secondly if you want to share methods functions across multiple pages you should make a seperate class to contain these public methods or functions. just right click on the project and hit new item, then you will see class listed. Put all your shared functions/methods in it and call them as needed from your pages. I do this all the time with image resizers, shipping modules, credit card gateways etc. If you need any more help let me know.

first of all it is best to use only one file - not 3
one of the best practise is not to duplicate - code, controls - if you can modify them
so in your case you can use only one page and fr the aditional coding to use user control

the aditional coding will be in the page_load of the page ( aspx file ), and the page_load of the user control is executed after the page_load of the aspx file is finished

Ok... I see. I have studied a little on user controls but never actually made one. With user controls, can you encapsulate what would normally be inside a page_load inside the usercontrol instead? Like:

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